(a) Field of the Invention
The present invention relates to a cathode ray tube, more particularly, to a cathode ray tube having an improved funnel, on which the deflection yoke is mounted, capable of decreasing deflection power.
(b) Description of the Related Art
In a well-known cathode ray tube, electron beams emitted from an electron gun assembly are deflected to a phosphor screen in a horizontal and vertical direction. The electron beams impinge on a corresponding phosphor pixel, resulting in emission of light to form images or characters.
Cathode ray tubes are mainly installed in color televisions or computer monitors to be provided to consumers. Recently, cathode ray tubes have been enhanced to be installed in High-Definition televisions (HDTV).
In order to cope with OA equipment, e.g., an HDTV or monitor for a PC, either the deflection frequency must be increased, or the anode voltage for finally accelerating the electron beams must be increased. An increase in anode voltage and an increase in deflection frequency cause an increase in deflection power, i.e., an increase in consumption power of the deflection yoke.
In order to solve these problems, the neck diameter of conventional cathode ray tubes has been decreased, and the deflection magnetic field generated from the deflection yoke is likely to approach the trajectories of the electron beams so that the deflection power efficiency can be improved.
However, since the neck diameter is decreased, it is difficult to manufacture the cathode ray tube, and the focus characteristics of the electron gun assembly are deteriorated.
Therefore, in another conventional cathode ray tube, the neck diameter is maintained (about xcfx8629.1 mm), but the outer diameter of the funnel near the neck side is decreased, so that the deflection power is reduced. However, when an electron beam is deflected in a direction along the maximum size of the screen, i.e., along the diagonal direction, the electron beam passes close to the inner surface of the funnel near the neck side on which the deflection yoke is mounted. This situation is called a BSN (Beam Strikes the Neck) problem. For this reason, the resultant image is not properly formed.
In this cathode ray tube, since the neck diameter is simply decreased through the experience of a designer or trial and error, it is difficult to effectively solve the BSN problem. Accordingly, it is difficult to decrease the deflection power.
In view of the prior art described above, it is an object of the present invention to provide a cathode ray tube capable of reducing the deflection power while preventing a BSN problem.
To achieve this object, as embodied and broadly described herein, the invention comprises
a panel, a phosphor screen being arranged on an inner surface of the panel;
a funnel having a deflection yoke on an outer periphery thereof, including:
a body connected to the panel; and
a cone connected to the body; and
a neck, connected to the cone of the funnel, having an electron gun disposed therein. The cone has a deflection power reducing shape which is formed to have a range of length 0.25xc3x97L from an end of the cone at the neck where L is an entire length of the cone measured along an axis of symmetry of the cathode ray tube.
According to an aspect of the present invention, the deflection power reducing means is formed in such a manner that the outline of the cone has a shape of an arc on a range of the length 0.25xc3x97L from the end of the cone at the neck as viewed in a cross section perpendicular to the axis of symmetry and satisfies the following conditions:
|Cz| less than 4.5 mm
25 mm less than r1 less than 50 mm
where Cz is a coordinate of a center of the aforementioned arc; and
r1 is a radius of curvature of the arc.
According to another aspect of the present invention, the deflection power reducing means is formed in such manner that the outline of the cone has a curvature on a range of the length 0.25xc3x97L from the end of the cone at the neck as viewed in a cross section perpendicular to the axis of symmetry and satisfies the following conditions:
0.26 less than R less than 0.43
where R is an average variation of height measured from the axis of symmetry to the each point of the curvature.
Both foregoing general description and the following Detailed Description are exemplary and are intended to provide further explanation of the invention as claimed.